Pulsed Carbon Dioxide Laser for Cartilage Vaporization and Subchondral Bone Perforation in Horses Part II: Morphologic and Histochemical Reactions

A pulsed carbon dioxide laser was used to vaporize articular cartilage in four horses, and perforate the cartilage and subchondral bone in four horses. Both intercarpal joints were examined arthroscopically and either a 1 cm cartilage crater or a series of holes was created in the third carpal bone of one joint. The contralateral carpus served as a control. After euthanasia at week 8, the treated and control joints were examined for gross changes, and samples of cartilage and subchondral bone, synovial membrane, and peripheral lymph nodes were examined histologically. Depletion of cartilage matrix glycosaminoglycan was assessed by safranin-O histochemical staining of the laser site and adjacent cartilage. Cartilage removal by laser vaporization resulted in rapid regrowth, with fibrous and fibrovascular tissue and occasional regions of fibrocartilage at week 8. The subchondral bone, synovial membrane, and draining lymph nodes appeared essentially unaffected by the laser cartilage vaporization procedure. Conversely, carbon dioxide laser drilling of subchondral bone resulted in poor penetration, extensive areas of thermal necrosis of bone, and significant secondary damage to the apposing articular surface of the radial carpal bone.     

Permanent Tracheostomy in Standing Horses: Technique and Results

Permanent tracheal stomas were created in seven sedated, standing horses with severe upper airway obstruction. After local anesthesia, a 3-cm by 6-cm rectangle of skin was removed from the ventral surface of the neck, 3 cm distal to the cricoid cartilage. The sternothyrohyoideus muscles were clamped proximally and distally, then transected to expose the tracheal rings. The ventral third of four tracheal rings was dissected from the tracheal mucosa that was then incised in a double "Y." Two layers of suture were used to achieve mucocutaneous closure. Stomas healed without serious complications; two mares subsequently foaled, and three horses were used for riding.     

Arthroscopic Subchondral Bone Plate Microfracture Technique Augments Healing of Large Chondral Defects in the Radial Carpal Bone and Medial Femoral Condyle of Horses

OBJECTIVE: To evaluate the effect of arthroscopic subchondral bone microfracture on healing of large chondral defects in horses. STUDY DESIGN: Short- (4 months) and long-term (12 months) in vivo experimental chondral defect model. ANIMALS: 10 horses, aged 2 to 5 years. METHODS: Each horse had a 1 cm2 full-thickness chondral defect created in both radial carpal bones and both medial femoral condyles. One carpus and one femoral condyle of each horse had the subchondral bone plate under the defect perforated using an orthopedic awl. All horses were exercised, five horses were evaluated after 4 months and five horses after 12 months. Gross, histologic, and histomorphometric examination of defect sites and repair tissues was performed, as was collagen typing of the repair tissue. RESULTS: On gross observation a greater volume of repair tissue filled treated defects (74%) compared with control defects (45%). Histomorphometry confirmed more repair tissue filling treated defects, but no difference in the relative amounts of different tissue types was observed. There was an increased percentage of type II collagen in treated defects compared with control defects and evidence of earlier bone remodeling as documented by changes in porosity. CONCLUSIONS: In full-thickness chondral defects in exercised horses, treatment with subchondral bone microfracture increased the tissue volume in the defects and the percentage of type II collagen in the tissue filling the defects when compared to nontreated defects. CLINICAL RELEVANCE: No negative effects of the microfracture technique were observed and some of the beneficial effects are the basis for recommending its use in patients cases with exposed subchondral bone.     

Mandibular Condylectomy Technique and Results in Normal Horses

A technique of mandibular condylectomy and menisectomy is described. Unilateral condylectomy and menisectomy were performed in two horses, and two horses were treated by bilateral condylectomy and unilateral meniscectomy. Minor temporary alterations in mastication occurred following unilateral condylectomy; more severe and longer lasting abnormalities of prehension and mastication occurred following bilateral condylectomy. Malocclusion occurred in all horses following surgery but was only clinically significant in one horse that developed occlusion of the lower incisor teeth 3 mm caudal to the upper incisor teeth following bilateral condylectomy. Maximal mouth opening was normal following unilateral condylectomy and increased following bilateral condylectomy, both immediately following surgery and after 16 weeks. Maximal lateral deviation of the mandible was increased immediately following unilateral and bilateral condylectomy; 16 weeks following surgery one joint had increased, and two had normal and three had decreased maximal lateral deviations. On radiographic, gross, and histological evaluation, the condylectomy sites underwent remodelling and bony proliferation to produce "pseudo" condyles. At necropsy, 16 weeks following surgery, five of the six operated temporomandibular joints contained fibrous tissue with single or multiple cavities lined by synoviocytes. The nonoperated temporomandibular joints were normal. Functional use of the mandible was good in three horses; the fourth horse developed significant malocclusion and had satisfactory function following bilateral condylectomy.     

Triangulated Flap Technique for Nasofrontal Surgery Results in Five Horses

A modified bone-flap technique was used to expose space occupying lesions that involved the conchofrontal sinus, ethmoturbinates, and caudal nasal cavity in five horses. The most common clinical findings were chronic nasal discharge and upper airway obstruction. Surgical intervention was based on endoscopic and radiographic interpretation. The triangulated bone-flap technique increased surgical exposure to the conchofrontal sinus by almost twice the area observed in previously described surgical techniques. The major advantages were that this technique allowed excellent visualization, thorough palpation, and surgical manipulation within the sinus and associated structures. Complications were minimal. One horse was euthanized 1 month postoperatively with recurrence and spread of a mycotic granuloma. The technique extended the usefulness of the other four horses in a 9 to 24 month follow-up period, although the obstructing lesion recurred after 2 years in one of the four horses.     

The Reliability of Endoscopic Examination in Assessment of Arytenoid Cartilage Movement in Horses Part I: Subjective and Objective Laryngeal Evaluation

Videorecordings of the laryngeal activity of 108 unsedated horses were obtained at rest by passing a flexible videoendoscope into the nasopharynx through the right ventral meatus. All videotaped images were reviewed once, and 72 were reviewed twice, by three veterinarians. Laryngeal cartilage movement was assessed subjectively with a five-tier grading system. The mean intraobserver agreement was 83.3% (range, 75.0%-90.2%) with a kappa statistic of .65 to .98. The mean interobserver agreement was 79.0% (range, 70.4%-80.6%) with a kappa statistic of .51 to .90. A computer program was developed to measure the left:right ratio of the rima glottidis. The mean left:right ratio for horses assigned a median laryngeal grade of I was 0.84 (range, 0.55-1.03); for grade II, 0.82 (0.50-1.12); for grade III, 0.59 (0.39-0.91); and for grade IV, 0.24 (0.07-0.35).     

Osteostixis for Incomplete Cortical Fracture of the Third Metacarpal Bone: Results in 11 Horses

Eleven horses with acute or chronic incomplete cortical fractures of the left or right third metacarpal bone (McIII) were treated with surgical puncture (osteostixis). The fractures were diagnosed by physical examination and radiography. Four to eight holes, 2.7 or 3.5 mm in diameter, were drilled in the fractured bone. Radiographically, the fractures were healed by month 3, and the drill holes were inapparent by month 7. Nine horses (82%) returned to race competition, and two horses were retired, one the result of a surgical complication. The mean time between surgery and the first race was 9.4 months. None of the bones refractured within 24 months of surgery. Osteostixis was not technically difficult and a second operation for implant removal was not necessary.     

Effects of Carbon Dioxide Insufflation and Body Position on Blood Gas Values in Horses Anesthetized for Laparoscopy

The objective of the study was to describe the effects of carbon dioxide pneumoperitoneum and Trendelenburg position on arterial blood gas values in horses anesthetized for laparoscopy. The study design was a prospective case series using 14 healthy adult horses anesthetized for elective laparoscopic surgery. All horses in the study were maintained under anesthesia with halothane in oxygen with intermittent positive-pressure ventilation. A pneumoperitoneum of 15 mmHg or less was achieved with carbon dioxide, and horses were tilted to a 35-degree Trendelenburg position to allow the completion of laparoscopic cryptorchidectomy (n = 13) or ovariectomy (n = 1). Heart rate, mean arterial pressure, and arterial blood gases were recorded at six time intervals throughout the procedure. Results of the study indicated a pH that decreased and partial pressure of carbon dioxide (PaCO₂) and mean arterial pressure that increased over time and differed significantly from baseline during Trendelenburg position. Partial pressure of oxygen (PaO₂) was significantly lower than baseline after assumption of Trendelenburg position and did not improve on return to normal recumbency and abdominal pressure. As body weight increased, pH and PaO₂ decreased and PaCO₂ increased. We concluded that horses placed in Trendelenburg position have changes that are transient, with the exception of PaO₂. Heavier horses have a greater change in pH, PaCO₂, and PaO₂ than lighter horses during abdominal insufflation and Trendelenburg position. The changes incurred during CO₂ abdominal insufflation and Trendelenburg position are transient, with the exception of a decreased PaO₂. Heavy horses undergoing abdominal insufflation and Trendelenburg position should be closely monitored for critical cardiopulmonary values.     

Holmium:YAG Laser Lithotripsy for Urolithiasis in Horses

Background: Laser lithotripsy has been used as an alternative to surgical removal of uroliths.
Objective: To describe the procedure and efficacy of laser lithotripsy for removal of lower urinary tract uroliths in horses. Additionally, the ultrastructure and the differences in mineralogy and microstructure from 1 successful and 1 unsuccessful laser lithotripsy case are described.
Animals: Six client-owned horses with 7 episodes of naturally occurring urocystoliths, urethroliths, or both.
Methods: Retrospective study of all horses treated between 2006 and 2008 by laser lithotripsy. All horses were sedated followed by laser lithotripsy. Quantitative urolith analysis was performed in all cases. Ultrastructure and microstructure analyses were performed on uroliths from 2 horses.
Results: Procedural success was achieved in 5 of 7 laser lithotripsy procedures. No complications occurred as a result of laser lithotripsy. One horse developed uroabdomen likely as a result of manual lithotrite disruption of the bladder after failure of laser lithotripsy. There were differences in microstructure between 1 urolith that was successfully fragmented by laser lithotripsy and 1 urolith that was resistant to laser fragmentation.
Conclusions and Clinical Importance: Laser lithotripsy is an effective procedure for removal of some urocystoliths, urethroliths, or both in horses.     

Ethylene Oxide Sterilization of Cortical Bone for Bone Banking Technique and Results in Three Dogs and One Cat

A protocol for clean harvesting, ethylene oxide sterilization, and room temperature storage of canine and feline cortical bone for use as allografts in fracture repair is described. Three dogs and one cat received cortical allografts prepared in this manner for reconstruction of severely comminuted mid-diaphyseal femoral fractures. Function of the affected limb returned to normal, and radiographic evaluations of the allografted femurs showed union at the host-graft interface and incorporation of the allograft.     

Esophageal Disorders in 61 Horses: Results of Nonsurgical and Surgical Management

Obstructive esophageal disorders in 61 horses included feed or foreign body impaction (27 horses), strictures (18 horses), perforations (11 horses), and diverticula (5 horses). Horses with feed impaction were treated nonsurgically (25 horses) or by esophagotomy (2 horses). Survival to discharge was 78%, and 37% of these had persistent chronic obstruction at home. Long-term survival was 52%. Long-term survival of nine horses treated nonsurgically for esophageal strictures was 22%; for nine horses treated surgically it was 44%. Long-term survival of horses treated nonsurgically was significantly better in acute than chronic strictures. Surgical repair of esophageal mural strictures was more successful than repair of annular or mucosal strictures. One third of the horses with strictures were foals. Long-term survival for horses with strictures was 33%. Long-term survival was higher for the horses with perforations managed surgically (2 of 4) than nonsurgically (0 of 7). Long-term survival for this group was 18%. One esophageal diverticulum was managed nonsurgically, and four were treated surgically; all horses survived long term. Complications of obstructive esophageal disorders included aspiration pneumonia, chronic obstruction, esophageal mucosal ulceration, postoperative infection, pleuritis, laminitis, laryngeal paralysis, and Horner's syndrome.     

A Modified Technique for Extensive Large Colon Resection and Anastomosis in Horses

Objective —To describe an alternative technique for large colon resection and anastomosis in horses.
Study Design —Retrospective study of clinical patients.
Animal Population —37 horses that had ventral midline celiotomies between July 1, 1990, and July 1, 1994.
Methods —Large colon resection and anastomosis was performed using a modification of previously described techniques. Modifications include mesocolon ligation with a stapling device and an end-to-end apposition of the right ventral and right dorsal colon.
Results —Twenty-one of the 37 horses were discharged from the hospital without complications. Two horses were euthanatized immediately after recovery from anesthesia because of hindlimb fracture. Fourteen horses were euthanatized in the initial postoperative period because of persistent endotoxemia and abdominal pain.
Conclusions —The described technique is a safe, reliable method for large colon resection and anastomosis in horses.
Clinical Relevance —The described technique is fairly simple to perform and requires less surgical time compared with other techniques.     

Autogenous Cancellous Bone Grafts From the Sternum in Horses Comparison With Other Donor Sites and Results of Use in Orthopedic Surgery

Cancellous bone was collected from the fourth or fifth sternebra of six horses aged 12 to 36 months, and compared quantitatively and qualitatively with cancellous bone collected from the tuber coxa, proximal tibia, and rib at the time of necropsy, 28 to 49 days after surgery. Cancellous bone collected from the sternum was equivalent in amount and in microscopic appearance to that collected from the other three sites.
Cancellous bone also was collected from the sternum for use during clinical orthopedic surgery in 18 horses. Wound dehiscence occurring in two horses healed uneventfully by second intention. In each horse, an adequate amount of cancellous bone was obtained from one sternebra, with the exception of one horse where cancellous bone from two sternebra was used. Major complications with the donor sites were not encountered.     

Carbon Dioxide Laser Keratectomy as a Treatment Option for Equine Corneal Stromal Abscessation: A Comparison to Lamellar Keratectomy and Penetrating Keratoplasty

Carbon dioxide (CO₂) laser keratectomy was compared to lamellar keratectomy (LK) and penetrating keratoplasty (PK) as a potential treatment option for equine corneal stromal abscessation. The medical records of 35 client owned horses undergoing surgical management of stromal abscessation were reviewed. Among those 17 underwent LK, 3 PK and 15 CO₂ laser keratectomy. Healing of the stromal abscess was achieved in all treated eyes. Those horses undergoing CO₂ laser keratectomy demonstrated few complications, and the time to healing and cosmetic outcome was comparable to those horses undergoing LK and PK.     

The Reliability of Endoscopic Examination in Assessment of Arytenoid Cartilage Movement in Horses Part II. Influence of Side of Examination, Reexamination, and Sedation

Twenty Thoroughbred and Standardbred horses underwent endoscopic evaluation of arytenoid cartilage movement twice within 1 week. Each time, a flexible endoscope was passed without sedation through the right nostril and the left nostril, and through the right nostril 5 minutes after administration of xylazine hydrochloride (0.55 mg/kg or 1.1 mg/kg intravenously). Laryngeal cartilage movement was videorecorded. All videotaped images were reviewed by three veterinarians and subjectively placed in one of four grades. The intraobserver agreement rate varied from 52.6% for examination under sedation with 1.1 mg/kg of xylazine to 89.5% for unsedated reexamination through the left nostril. The effect of the various observations on median laryngeal grade was calculated. Examination under xylazine hydrochloride at either dosage yielded a change in median laryngeal grade from the unsedated examination in 45% of the evaluations. Reevaluation through the right or left nostril resulted in a different median laryngeal grade in 21% and 5% of the examinations, respectively. Objective measurements of the rima glottidis obtained by computer-assisted morphometric analysis of the recorded laryngeal images allowed laryngeal images to be dichotomized regardless of the condition of endoscopic examination. Endoscopic evaluation of laryngeal cartilage movement is subjective and is influenced by sedation with xylazine, evaluation through the alternate nostril, and different day of examination. The most consistent evaluation was obtained during repeated examination through the left nostril.     

Holding Power of Orthopedic Screws in Equine Third Metacarpal and Metatarsal Bones: Part I. Foal Bone

The holding power of orthopedic screws in the third metacarpal and metatarsal cadaver bones of foals that were aged from 1 to 14 days was tested. Comparative trials between screws inserted at the same site in contralateral bones from the same foal were performed to compare the holding power of 5.5 mm cortical and 6.5 mm cancellous screws in the metaphysis, and the holding power of 5.5 and 4.5 mm cortical screws in the diaphysis. A MTS servohydraulic tensile testing machine was used to perform screw pullouts at a displacement rate of 19 mm/sec. There was no significant difference between maximum holding power of 5.5 mm cortical screws and 6.5 mm cancellous screws in the metaphysis when expressed as kg per mm of bone width at the screw insertion site (p = 0.097) or as kg per mm of screw thread engaged in the bone (p = 0.17). There was no significant difference in holding power of 5.5 and 6.5 mm screws in the proximal versus distal metaphysis (p = 0.10). The 5.5 mm screws had significantly greater holding power than the 4.5 mm screws in the diaphysis (p = 0.0097). Fixation failure at screw pullout was always due to bone shear. In internal fixation in foal bone, the 5.5 mm screws may be a suitable alternative to 6.5 mm screws in the metaphysis. Use of 5.5 mm rather than 4.5 mm screws is recommended in the diaphysis because of greater holding power.     

Cemented Total Knee Replacement in 24 Dogs: Surgical Technique, Clinical Results, and Complications

Objective— To characterize the performance of cemented total knee replacement (TKR) in dogs.
Study Design— Preclinical research study.
Animals— Skeletally mature, male Hounds (25–30 kg; n=24) with no preexisting joint pathology.
Methods— Dogs had unilateral cemented TKR and were evaluated at 6, 12, 26, or 52 weeks (6 dogs/time point) by radiography, bone density analysis, visual gait assessment, and direct measurement of thigh circumference and stifle joint range of motion as indicators of functional recovery. At study end, the stability of the cemented tibial component was determined by destructive mechanical testing.
Results— Joint stability was excellent in 16 dogs (67%) and good in 8 dogs. None of the tibial components had evidence of migration or periprosthetic osteolysis whereas 1 femoral component was loose at 52 weeks. There was an early and significant decrease in tibial bone density, likely because of disuse of the operated limb. Dogs returned to full activity by 12 weeks. The tibial cement–bone interface maintained its strength over 52 weeks.
Conclusions— Cement provides stable fixation of the tibial component in canine TKR.
Clinical Relevance— Cemented TKR yields adequate clinical function and stifle joint excursion in the dog. Clinical studies are needed to determine the long-term fate of cemented TKR implants, to assess the influence of implant design on implant fixation and wear, and to obtain objective functional data.     

The Intercarpal Ligaments of the Equine Midcarpal Joint, Part 3: Clinical Observations in 32 Racing Horses With Midcarpal Joint Disease

Objective— To characterize the clinical features of intercarpal ligament pathology and to determine the relationship among palmar intercarpal ligament tearing, dorsomedial intercarpal ligament (DMICL) hypertrophy, and other intraarticular lesions.
Study Design— Prospective clinical observations.
Animals or Sample Population— Twenty-eight thoroughbred and four standardbred race horses.
Methods— Clinical, radiographic, and arthroscopic examination of 53 midcarpal joints of 32 horses.
Results— Palmar intercarpal ligament tearing was observed in 30 joints of 22 horses. Some tearing of the medial palmar intercarpal ligament (MPICL) was present in 27 joints of 20 horses, and tearing of the lateral palmar intercarpal ligament in 9 joints of 7 horses. There was no correlation between the severity of clinical signs recorded and the degree of MPICL tearing. Joints with grade 2–4 MPICL tearing had significantly less cartilage and bone damage than joints with grade 1 or no ligament damage ( P <.05). There was a significant inverse relationship between the number and size of intra-articular fractures, as assessed radiographically, and ligament damage ( R = -.31). The DMICL was identified in all joints, and in 18 joints the ligament was enlarged. There was a significant correlation between MPICL damage and hypertrophy of the DMICL ( R =.35). There was no correlation between DMICL hypertrophy and articular cartilage damage or subchondral bone damage.
Conclusions— Severe subchondral bone and MPICL damage rarely occur in the same joint and DMICL hypertrophy may be associated with, rather than a cause of, joint disease.
Clinical Relevance— There are no clinical or radiographic findings that will differentiate intercarpal ligament injury from other carpal injuries. Diagnosis is only possible by arthroscopic examination of the midcarpal joint.     

Nanoparticulate CpG Immunotherapy in RAO‐Affected Horses: Phase I and IIa Study

Background

Recurrent airway obstruction (RAO), an asthma‐like disease, is 1 of the most common allergic diseases in horses in the northern hemisphere. Hypersensitivity reactions to environmental antigens cause an allergic inflammatory response in the equine airways. Cytosine‐phosphate‐guanosine‐oligodeoxynucleotides (CpG‐ODN) are known to direct the immune system toward a Th1‐pathway, and away from the pro‐allergic Th2‐line (Th2/Th1‐shift). Gelatin nanoparticles (GNPs) are biocompatible and biodegradable immunological inert drug delivery systems that protect CpG‐ODN against nuclease degeneration. Preliminary studies on the inhalation of GNP‐bound CpG‐ODN in RAO‐affected horses have shown promising results.

Objectives

The aim of this study was to evaluate the clinical and immunological effects of GNP‐bound CpG‐ODN in a double‐blinded, placebo‐controlled, prospective, randomized clinical trial and to verify a sustained effect post‐treatment.

Animals and Methods

Twenty‐four RAO‐affected horses received 1 inhalation every 2 days for 5 consecutive administrations. Horses were examined for clinical, endoscopic, cytological, and blood biochemical variables before the inhalation regimen (I), immediately afterwards (II), and 4 weeks post‐treatment (III).

Results

At time points I and II, administration of treatment rather than placebo corresponded to a statistically significant decrease in respiratory effort, nasal discharge, tracheal secretion, and viscosity, AaDO ₂ and neutrophil percentage, and an increase in arterial oxygen pressure.

Conclusion and Clinical Importance

Administration of a GNP‐bound CpG‐ODN formulation caused a potent and persistent effect on allergic and inflammatory‐induced clinical variables in RAO‐affected horses. This treatment, therefore, provides an innovative, promising, and well‐tolerated strategy beyond conventional symptomatic long‐term therapy and could serve as a model for asthma treatment in humans.